Bilateral Cochlear Implants: Reasons, Research, and Support

At the “Play It By Ear!” seminar, audiologist Jace Wolfe, Ph.D., CCC-A (Hearts for Hearing) gave lots of fantastic information about bilateral implants as part of a larger presentation on developments in audiology. The information was so wonderful, and bilateral implants are such a “hot topic” right now, I decided that this subject deserved its own post. Here, you will find information on the pros and cons of bilateral CIs, information about the timing of bilateral implants, the discussion about bilateral CIs vs. bimodal amplification (one CI and one HA), and resources to help make the case to insurance companies for why bilateral cochlear implants deserve insurance coverage.

Benefits of Binaural (2 ear) Hearing:

Improved Localization: with two ears, you can tell where a sound is coming from and “localize” the source of the noise.

Improved Hearing in Noise: Studies have shown that going from one implant to two yields, on average, a 6dB improvement in hearing in noise, no matter the amount of time elapsed between implants. So, if with one CI you can hear sounds 6dB BELOW background noise, with your second, you should hear sounds about 12dB SOFTER than the noise around you. While 6dB might not seem like much, each decibel gained corresponds to about a 10% increase in your ability to hear in noise. So, being able to hear speech six decibels quieter than the noise around you translates into about a 60% improvement in your ability to detect and discriminate speech. That’s pretty impressive!

Improved Detection of Soft Sounds: this is called “summation” — a quiet sound in one ear sounds softer than a quiet sound in two ears, because the ears can “add up” what they hear to make soft sounds more audible

Optimal Access to Sounds from Each Side: you no longer have to position yourself so that your “good ear” faces the speaker or source of noise

Greater Ease of Listening

How late is too late? Is there a “critical window” for receiving a second cochlear implant? If both ears are CI candidates, then it is best to receive both implants as young as possible. But what about people who received cochlear implants years ago, when bilateral CIs were unheard of? Is it too late for them? NO! The older the age at implant of the “new ear”, the harder it will be to bring it up to the speech perception and performance level of the first ear. However, the SUM of the two ears leads to increased hearing in noise and localization ability no matter how long you waited between implants. Often, the sum of the two ears is far greater than simply adding the numbers for their individual performances — this just goes to show that our brains are equipped for binaural listening and, when given the appropriate input, they respond accordingly! Also, therapy for the “new ear” can greatly improve its speech perception abilities.

Is it better to have two cochlear implants or one cochlear implant and one hearing aid? IT DEPENDS. There is no cut-and-dried answer here because the choice of CI(s) and/or HA(s) is highly dependent upon each persons audiogram and performance on various tests. In a group of test subjects with similar levels of hearing loss, those with two cochlear implants were able to localize sound better than those with a hearing aid + a cochlear implant. Some bimodal (CI + HA) users showed evidence of a “bimodal disruption” — that is, even though the HA and CI worked well on their own, the signals together actually made localization and hearing in noise more difficult. Cochlear implants are better at providing the signals of a sound’s “amplitude envelope” — the aspects of sound that lead to speech recognition and melody recognition in music. Hearing aids are better at providing “fine structure clues” about the nature of sound. However, new HA and CI programming strategies are being developed every day so, while these maxims are generally true, much work is being done to increase both amplitude envelope and fine structure functionalities in both types of hearing devices.

What if insurance DENIES your request for bilateral cochlear implants? Here are some guidelines for your petition with appropriate research references to include which support bilateral cochlear implantation.

Improved localization is both a quality of life and a SAFETY concern. (Litovsky et al, 2006) (Nopp et al, 2004)

Unilateral hearing loss has detrimental social and educational effects. Children who have normal hearing in one ear and profound loss in the other are TEN TIMES more likely to fail a grade. While the cochlear implant provides great hearing, it is still not as good as the “real thing” so if children with normal hearing in one ear are ten times more likely to fail… children with only one CI and nothing in the other ear are at an even greater disadvantage. (Bess et al , 1986) (Lieu, 2004)

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Hi! I asked my audiologist about getting second CI would benefits me.. They said no to me since i have been uniliaterialy implanted for 25 years now. I recieved my Cochlear Implant when i was 5 years old. I was asking 2 people at different times. I am asl user but do use CI all the time. I do have listening skill but it is not best. I recently went in for remapping. I asked that question and audi shot it down so fast that she didnt considered that fact that i have Usher’s Syndroms. Its matter of safety and walking around with half head of sound and cannot tell where the sounds come from.. What can i do to convincing the AUDI to reconsiders m case? Or Should I see ENT to get more better direct answer?

It may be worth going to a different audiologist for a second opinion. While a second CI isn’t going to make you instantly into a listening and spoken language communicator, there are some real benefit to hearing with two ears, as you’ve stated — especially in the case of someone like you who is also at risk for vision loss. Perhaps it’s time to talk to your ENT and/or schedule an evaluation with a different audiologist or cochlear implant program. Best wishes!